Research On The Experimental Simulation And Scheme Optimization Of Traditional Restoration Technology For Ancient Timber Frame

Traditional timber buildings are precious architectural heritage and have important value of cultural protection and scientific research. The timber frame is connected by mortise-tenon joints, and because the mortise-tenon joint is not connected entirely, so the structural stiffness is weak for the resistance to deformation, and the frame is prone to loosening and slanting under the action of the long-term environmental erosion and external forces. Most the existing ancient timber frame buildings with various degree of tilt, therefore, the restoration and strengthening for the slanted timber frames is an important task of the protection of architectural heritage in China.It has been proved by the long-term engineering practice that the traditional technology of " Dajian-Bozheng" (Restoring to correct position by lifting and traction) is an optimal technology for the restoration and strengthening project. However, its implementation of construction technology has no systemic theoretical guidance, so its technical level remains in the stage of traditional experience.Under the direction of the key project of national natural science foundation of China (51338001), Condition assessment, safety limit and performance maintenance of the ancient timber frameworks, an ancient house of salt merchant in the Qing dynasty in Yangzhou city is as the research object, and the timber frame scale model is made. Aiming at five different slanted conditions, the research method combining the physical model test and finite element numerical simulation is applied. And the experimental simulation of restoration technology of "Dajian-Bozheng" and mechanical properties of timber frame are studied respectively. Main research work of this paper is included as follows.Firstly, according to the technology of "Dajian-Bozheng", the model tests for five different conditions of slanted timber frame are conducted. The reset condition and reset force system are real time monitored in the reset process of slanted timber frame, its focus on reset load and law of column grid and the elastic recovery performance of timber frame. The test results indicates that, timber frame restoration is involved in the connection of column grid and stiffness of column plane, the distance of column frame and the force transfer of connection components.The resetting procedure has an apparent influence on the elastic recovery of timber frame after restoration. In addition, non-uniform settlement of foundation has a greater influence on the deformation of timber frame in lateral direction of the column grid.Secondly, the finite beam element model of slanted timber frame was built by software ANSYS. The FE model has been set the 3-D spring elements in mortise-tenon joint connection of beam-column nodes. The stiffness parameters reflecting connection property are obtained by mechanical testing. So the connection of beam-column is simplified in the finite element model of timber frame construction. Based on the simulation of restoration process of reduced scale model, the results of numerical and model experimental values are roughly similar. So the established finite element model can be used in the simulation study of restoration scheme of slanted timber frame of ancient architecture.Finally, combining the experimental data and finite element simulation results, reset stress conditions of the timber frame under different loading schemes and restoration technologies are analyzed and compared. In accordance with the optimization goal of the "overall frame can be reset effectively and the stress increment of components is minimum", the "successive cyclic tension" reset technology is selected as the optimized scheme for the slanted timber frame.Based on physical model test and finite element numerical simulation, the research method on analysis and evaluation of mechanical performance of the slanted timber frame under restoration technology has been constructed, which can provide the useful reference for the scheme selection and safety assessment of repair projects for Chinese timber frames.